For years, the dream of an all-optical network has lain somewhere between Star Wars and a paper cup and a string. Recent successful work on the creation of an optical diode is a virtual case study in both the physics and materials sciences challenges of trying to develop all-optical networks. It is also a significant step towards their final realization.

One answer may be... garnet. Yes, the January birthstone.

The material that Ross and others in her field use is a synthetic, lab-grown garnet film. Similar to the natural mineral, often used as a gemstone, it is transparent in the infrared part of the spectrum. This makes synthetic garnet ideal for optical communications systems, which use the near infrared. Unlike natural garnet, it’s also magnetic.... While it works, it’s too big and too labor intensive for use as a commercial integrated chip. For that, you need to grow garnet on silicon. The challenge that Ross’s group overcame is that garnet doesn’t grow on silicon. When you start to talk about garnets as minerals, and not just the January birthstone, you find they are actually very complicated. 'You could find half the Periodic Table in garnet,' says Bethanie Stadler of the University of Minnesota, whose lab has also done pioneering work on magneto-optical garnet based isolators. She’s only partially joking.